1. Field of Invention
This invention relates to a feed apparatus for machine tools.
This invention further relates to feed apparatus for machine tools and more particularly to hydraulic barfeed apparatus for machine tools which have a moving headstock that moves the barstock back into the barfeed apparatus rapidly and advance it forward rapidly.
This invention specifically relates to a simple, but effective design that maintains a very stable pressure in the hydraulic system of barfeed apparatus for moving headstock machines.
2. Related Art
Barfeed devices for machine tools with a moving headstock have been commercially available for many years. In general they have been limited to gravity feed, however other methods including hydraulics and pneumatics have also been used.
The gravity type advances the bar toward the spindle with a chain or cable pulling a pusher of some type inside a guide tube, the cable or chain is pulled by a weight. Gravity feed designs are the least effected by rapid movement of a moving headstock machine but they are difficult to adjust and operate. While these designs have specific benefits, they are generally considered to be very limited by those skilled in the art, and generally require lower spindle speeds than other designs.
The hydraulic cylinder designs offer greater control and ease of adjustment but do not work well with machine tools with moving headstock. The pressure is adjusted manually and rapid travel of stock backwards into the feeder increase the pressure faster than it can be unloaded. The resulting increase in pressure increases vibration and noise, limiting the speed of the spindle, reducing productivity. In some cases the sudden increase in pressure causes lines to break and seals to leak. When the stock rapids forward the end of the bar can leave the support and guide of the pusher and the unguided bar end can be very dangerous. In designs that incorporate hydrodynamic support air can be trapped in the pusher resulting in insufficient fluid in the guide tubes, appreciable lessening the hydrodynamic support.